The invention relates to a changeable mounting of a sensing pin or of a sensing pin combination to the sensing head of a coordinate measuring machine, in which a clamping device draws the connecting body of the sensing pin or of the sensing pin combination into a bearing clearly determining its position in a receiving device on the sensing head.
Such mountings are installed in the sensing heads of polycoordinate measuring machines, so that in the change of the measuring assignment, especially in automatic measuring, a sensing pin adapted to the corresponding measuring assignment or a correspondingly adapted sensing pin combination can be rapidly changed.
German Pat. No. DE-OS 33 20 127 discloses a receiver for the changeable fastening of a sensing pin or a sensing pin combination to the sensing head of a coordinate measuring machine, in which an electrically operating clamping device draws the connecting body of the sensing pin or of the sensing pin combination against a bearing clearly determining its position in the receiver on the sensing head.
In this electrically operating clamping device it is a matter either of a small electric motor with a threaded spindle or of an electromagnet, with which the field of a permanent magnet is compensated or reinforced.
A disadvantage of these arrangements is that, in the first place, they are relatively heavy and thus increase the inert mass, unfavorable for rapid, positionally accurate movements of the sensing head and, in the second place, they emit heat in their operation, which in the case of frequent sensing pin changes has a disadvantageous effect both on the stopping accuracy of the sensing pins and also on the measuring accuracy.
Further, German Pat. No. DE-PS 35 26 108 discloses a receiver for the changeable fastening of a sensing pin or of a sensing pin combination to the sensing head of a coordinate measuring machine, in which a mechanical clamping mechanism acting on the connecting body of the sensing pin or sensing pin combination is used, in order to draw the pin against a bearing clearly determining its position in the receiver on the sensing head. This clamping mechanism, however, upon a collision between the sensing pin and the workpiece, does not disengage, so that there exists the danger that in the process the entire sensing head will be damaged.
Furthermore, Japanese patent abstract 58-37 501 (A) discloses a measuring head in which the shaft of a sensing pin is held over subpressure in a bore on the sensing head.
Aside from the possibility lacking hereof exactly defining the angular position especially of a sensing pin combination, with this sensing pin mounting, too, the sensing head can be damaged if through a wrong operation there occurs a collision between the sensing pin and the workpiece.
The problem of the invention, therefore, is to specify a mounting with which the clamping arrangement only increases by a small amount the inert mass of the mounting and in the operation of which there arises no heat burdening of the mounting. Simultaneously, the device must be economical in its manufacture and secure in operation.